Add the Share App system shortcut to the Go Launcher

This shortcut allows users to initiate peer-to-peer app sharing from an app's long-press menu on the home screen. It does so by passing an intent to the specified component. In this base implementation, that specification in config.xml is left blank, and the button will not appear. In GMS Launchers such as LauncherGoGoogle, the config should be set to point to Nearby Sharing.

This also establishes Launcher3QuickStepGo as a distinct subclass of QuickstepLauncher instead of merely a build configuration.

Bug: 157515296
Bug: 174286192
Test: Manual (tested on local wembley devices)
Test: m -j RunLauncherGoGoogleRoboTests
Change-Id: I826bd03721d2e7e963b15d5958e9a18a1cc16f1d
diff --git a/go/AndroidManifest-launcher.xml b/go/AndroidManifest-launcher.xml
new file mode 100644
index 0000000..2223036
--- /dev/null
+++ b/go/AndroidManifest-launcher.xml
@@ -0,0 +1,71 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+/*
+**
+** Copyright 2020, The Android Open Source Project
+**
+** Licensed under the Apache License, Version 2.0 (the "License");
+** you may not use this file except in compliance with the License.
+** You may obtain a copy of the License at
+**
+**     http://www.apache.org/licenses/LICENSE-2.0
+**
+** Unless required by applicable law or agreed to in writing, software
+** distributed under the License is distributed on an "AS IS" BASIS,
+** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+** See the License for the specific language governing permissions and
+** limitations under the License.
+*/
+-->
+<manifest
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    package="com.android.launcher3">
+    <uses-sdk android:targetSdkVersion="29" android:minSdkVersion="25"/>
+    <!--
+    Manifest entries specific to Launcher3. This is merged with AndroidManifest-common.xml.
+    Refer comments around specific entries on how to extend individual components.
+    -->
+
+    <application
+        android:backupAgent="com.android.launcher3.LauncherBackupAgent"
+        android:fullBackupOnly="true"
+        android:fullBackupContent="@xml/backupscheme"
+        android:hardwareAccelerated="true"
+        android:icon="@drawable/ic_launcher_home"
+        android:label="@string/derived_app_name"
+        android:theme="@style/AppTheme"
+        android:largeHeap="@bool/config_largeHeap"
+        android:restoreAnyVersion="true"
+        android:supportsRtl="true" >
+
+        <!--
+        Main launcher activity. When extending only change the name, and keep all the
+        attributes and intent filters the same
+        -->
+        <activity
+            android:name="com.android.launcher3.Launcher3QuickStepGo"
+            android:launchMode="singleTask"
+            android:clearTaskOnLaunch="true"
+            android:stateNotNeeded="true"
+            android:windowSoftInputMode="adjustPan"
+            android:screenOrientation="unspecified"
+            android:configChanges="keyboard|keyboardHidden|mcc|mnc|navigation|orientation|screenSize|screenLayout|smallestScreenSize|uiMode"
+            android:resizeableActivity="true"
+            android:resumeWhilePausing="true"
+            android:taskAffinity=""
+            android:exported="true"
+            android:enabled="true">
+            <intent-filter>
+                <action android:name="android.intent.action.MAIN" />
+                <category android:name="android.intent.category.HOME" />
+                <category android:name="android.intent.category.DEFAULT" />
+                <category android:name="android.intent.category.MONKEY"/>
+                <category android:name="android.intent.category.LAUNCHER_APP" />
+            </intent-filter>
+            <meta-data
+                android:name="com.android.launcher3.grid.control"
+                android:value="${packageName}.grid_control" />
+        </activity>
+
+    </application>
+</manifest>